1. Field of the Invention
The present invention generally relates to a fluid level maintaining assembly, and more specifically to a multi-point float valve with adjustable high and low level settings, the float valve capable of both providing a tight seal as between an inlet and outlet, and operating in a wide range of flow pressure environments.
2. Description of Related Art
Float valves are known and used in a number of different applications. For example, embodiments of the conventional float valve can be found in cooling towers, water reservoirs, swamp coolers, chillers, ice machines and make-up water tanks for boilers, just to name a few. The conventional float valve incorporates four basic elements: the valve, pivot, float arm and float. A valve operated in response to the float position permits flow from a fluid supply to the interior of a tank when the level drops below a predetermined level maintained by the valve. Typically, float valves are used to control the flow of water. Water in the tank normally is stored at a constant level through an automatic supply of water into the tank as required, and for this purpose the float valve can be employed such that the water supply automatically stops when a target level is reached.
Conventional float valves have a number of limitations when utilized in applications such as make-up water tanks and other applications used in connection with municipal water systems. The limitations are acute in low flow rate environments, as well as wide pressure range environments. As those in the art are well aware, a conventional float valve can not be counted on to guarantee and maintain a tight seal when closed, thus inhibiting float valve use in many critical applications. Further, conventional float valve operating pressures must be maintained within a limited range or the valve will not work properly. Additionally, in many situations, current float valves just cannot be used, and, thus, other more complicated and expensive devices are used. Yet another problem with the float valve is its single point, level adjustment. Lastly, the float arm is easily broken through leaking or level bouncing (especially in boiler make-up water tanks).
The conventional float valve simply cannot provide leakproof sealing. The valve partially opens as soon as the float falls down from a target level. Once the level falls, the slightest drop of the float arm triggers the partial opening of the valve. The valve remains partially open until the float gains enough force to overcome the valve pressure. Under these conditions, small foreign particles are easily trapped between the valve and the valve seat. These foreign particles can create a scar on the valve and valve seat, or stick (weld) together on the valve and valve seat. Once this happens, leaking begins and the valve must be replaced. Even if there is enough force to close the valve, it will continue to leak.
The operating pressure range of the conventional float valve is limited, and bounded at an upper pressure by the weight of the float and the length of the float arm. Yet, the above-listed four elements of the typical float valve are usually fixed and cannot be adjusted or interchanged. Thus, a new float valve must be used each time the operating pressures change.
If the operating pressure is increased, the valve closing force must be increased. To increase the valve closing force, either the float arm length must be increased or the float weight must be increased. The assembly's resistance to line pressure is the product of the weight of the float and the length of the float arm. To provide a leakproof seal at high pressures, a float valve assembly must incorporate either a float of excessive weight, or an arm of excessive length, or both. Yet, the float valve environment rarely if ever can accommodate such a heavy float or lengthy arm. Thus, a float valve is not suitable for high pressure uses.
The conventional float valve also cannot work with low flow rates. Generally, the flow rate is determined by the coefficient of velocity. The higher coefficient of velocity, the higher the flow rate. Higher flow rate is in proportion to the area. Most of the float valve is partially or fully open under normal working conditions. When the valve is partially open, the coefficient of velocity is very low. When the valve is fully open, the coefficient of velocity is high. The actual opening port size is much smaller than the valve size. Thus, the conventional float valve cannot operate properly with an inadequate flow rate.
Additionally, the conventional float assembly has only one adjustment setting, typically the adjustment of the high level. This limits the functional range of the float valve.
Furthermore, the float arm of the conventional float valve is easily broken because of leaks or level bouncing. If the valve is leaking, the fluid level will pass the target level each cycle. Also, if the level is bouncing by any physical force, the level will pass the target level each cycle. Both of these situations create excessive buoyancy forces. These forces bend and distort the float arm, and can harm the valve seal. When the level begins to drop, the float arm will return to its original shape. Yet, if this type of bending happens repeatedly, for example, over a thousand times, a weak section of the float arm will break. Not only will this excessive force permanently damage the valve and valve seat, the valve life will be shortened drastically.
From the above observations regarding the limitations of prior art float valve assemblies, it is apparent that an improved float valve is needed to provide multi-point adjustment and more secure sealing capabilities through a wider range of operating pressures and flow rates. It is to the provision of such a valve assembly that the present invention is primarily directed.